netdev - Re: [PATCH bpf-next] bpf: use VM_MAP instead of VM

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Date:   Mon, 31 Jan 2022 17:28:45 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Hou Tao <hotforest@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andrii@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org, houtao1@...wei.com
Subject: Re: [PATCH bpf-next] bpf: use VM_MAP instead of VM_ALLOC for ringbuf

On 1/31/22 12:46 PM, Hou Tao wrote:
> Now the ringbuf area in /proc/vmallocinfo is showed as vmalloc,
> but VM_ALLOC is only used for vmalloc(), and for the ringbuf area
> it is created by mapping allocated pages, so use VM_MAP instead.
> 
> After the change, ringbuf info in /proc/vmallocinfo will changed from:
>    [start]-[end]   24576 ringbuf_map_alloc+0x171/0x290 vmalloc user
> to
>    [start]-[end]   24576 ringbuf_map_alloc+0x171/0x290 vmap user

Could you elaborate in the commit msg if this also has some other internal
effect aside from the /proc/vmallocinfo listing? Thanks!

> Signed-off-by: Hou Tao <houtao1@...wei.com>
> ---
>   kernel/bpf/ringbuf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
> index 638d7fd7b375..710ba9de12ce 100644
> --- a/kernel/bpf/ringbuf.c
> +++ b/kernel/bpf/ringbuf.c
> @@ -104,7 +104,7 @@ static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
>   	}
>   
>   	rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
> -		  VM_ALLOC | VM_USERMAP, PAGE_KERNEL);
> +		  VM_MAP | VM_USERMAP, PAGE_KERNEL);
>   	if (rb) {
>   		kmemleak_not_leak(pages);
>   		rb->pages = pages;
>